Reflecting electric lamp



Nov. 22, 1949 L. H. VERBEEK x-:TAL 2,483,751

-REFLEGTING ELECTRIC LAMP I Filed Feb. 25, 1949 Leo H. Verbeek, Gerardus H. Gerflsma, DH MC. A/

Theird Abomeg.

Patented Nov. 22, 1949 i BJEFLECTING ELECTRIC LAMP Leo Henricus Verbeek and Gerardus Herman Gerrltsma, Eindhoven, Netherlands, asslgnors to General Electric Company, a corporation of New York Application February 23, 1949, Serial N0. 77,782

In the Netherlands March 5, 1948 3 Claims. (Cl. 176-34) Our invention relates in general to electric incandescent lamps of the self-contained reflecting type adapted to project a beam of light.

Electric incandescent lamps .are known in which the bulb consists of a reflecting rear portion of ellipsoidal shape and a .reflecting front portion of spherical shape, with a concentrated incandescent filament located in the near focal point of the ellipsoidal bulb portion. Such lamps are especially suitable for projection purposes, in spotlights, and, in general, in combination with an optical system. In these lamps a window is normally provided in thevcenter of the mirror on the reflecting spherical -front portion of the bulb, through which window the light is transmitted to the outside. The base of the lamp is mountedat the opposite side of the bulbon the elliptical or rear section thereof.

In such lamps it has been attempted to gather as much as possible of the available light stream from the filament and to re-d-irect the same to the picture image located at the second or remote focal point of the `elliptical reflector section of the bulb. This picture image is normally loca-ted near the window in the mirror on the spherical portion of the bulb. In spite of this, however, it has been found that with the known type of incandescent lamps of this character, the amount of light actually transmitted is materially less than that available for transmission, and

besides, an appreciable amount of stray light is produced.

It is an object, therefore, of lour invention to provide an improved electric incandescent lamp of the above type having'increased light-radiating eiciency and reduced stray light.

In accordance with the invention, the abovementioned objects are obtained by constructing the lamp with its lead-in wires passing and sealed through the spherical front portion of the bulb, preferably at locations on diametrically opposite sides and outwardly of the window in the mirror on said front portion.

Further objects and advantages of our invention will be apparent from the accompanying description of a species thereof and from the accompanying drawing the single figure of which is a view, in cross section, of an electric incandescent, lamp comprising our invention.

Referring to the drawing, the lamp there shown is of the general type described and claimed in U. S. Patents 2,148,314 and 2,148,315, D. K. Wright, and comprising a bulb or envelope I consisting of a rear preformed concave recctor section 2 and a front preformed cover section 3 Athe light-transmitting Window I4 thereof.

2 which are fusion-sealed together to form the bulb. The two bulb sections 2 and 3 are made of pressed glass and are provided at their rims with outwardly extending flanges 4 and 5, respectively, having upstanding sealing ridges 6 and 'I which are fusion-scaled together. The inner-surface 8 of the rear reflector section 2 is coated with a suitable reflective metallic coating 9, such as aluminum or silver, and is of ellipsoidal or other similar shape such as to redirect into a converging beam of light, or through the remote-focus F2 of said surface, the light rays from a concentra-ted light source I0, such as a coiled tungsten lament, located approximately at the near focus F1 of the said surface. The ellipsoidal reflecting surface 9 of the rellector section 2 terminates approximately in the region of its focal plane f-f. An exhaust tubulation II is provided at the apex of the rear reector section 2 for exhausting and, if desired, gas-lling the lamp envelope, after which operations. the said tubulaticn is tipped-off in the Lnaxgner shown to thereby hermetically seal the The inner surface I2 of the front or cover section 3 is likewise provided with a reflective metallic coating I3 similar to the coating 9 andis of spheroidal shape with its center of curvature approximately coincident with the near focus F1 `of the ellipsoidal reflecting surface 9 so as to return the light rays from the light source I0 back through the focus F1 and onto the reilecting surface 9 of the rear reector section 2. The spheroidal reflecting surface I3 of the front section 3 is formed to a diameter substantially corresponding to that of the mouth of the ellipsoidal reecting surface 8 and it extends substantially right up to the rim of the said reflecting surface AIl-so as to form therewith a more or less continuous and uninterrupted reflecting surface. The central area of the spheroidal inner surface I2 of the front section 3 is left uncoated to form a clear light-transmitting window I4 preferably of circular shape and of large enough diameter to permit passage therethrough of substantially the full cone of light reflected from the ellipsoidal rear reflector 2.

In accordance with the invention, the two leading-in wires I5, I6 for the lamp are sealed through the front section 3 of the bulb at points on diametrically opposite sides and outwardly of As shown, the leading-in wires I5, IB extend into the bulb in a direction parallel to the axis a-a of the reilecting surface 9 and are sealed through thickened wall portions or bosses I1, I8 Provided 0D the front section 3 of the bulb. The metallic reecting coating I3 on the spherical front section 3 of the bulb is left of! those areas of the inner surfaces thereof immediately surrounding the leading-in wires I .5, I6 so as not to cause short-circuiting of the latter. Inwardly of the bulb, the leading-in wires I5, I6 are bent at right angles to the axis a-a of the reecting surface 9 and are connected to and support the opposite ends of the filament I which, in the particular case illustrated, is of the bar type and extends transversely to the reflector axis a--a and is approximately centered at the near focal point F1 of the reflector section 2.

By sealing the leading-in wires I5, I6 through the cover or front portion 3 of the bulb, instead of the rear portion 2 as has been customary heretofore, the rear or main reflecting surface 9 ofV the bulb is interrupted only by the very small opening I 9 required for the exhaust tubulation I I. Thediameter of this exhaust opening I9 need not be over 2 or 3 mm. Furthermore, this exhaust opening I9 is located in the optical axis a-a of the ellipsoidal reector 2 directly behind the lament I0, in a region which is not very active optically.

'Although the invention has been shown and described as applied to a lamp having a bulb. or envelope formed o'flpressed glass sections fused together, it will be obvious that such a type of bulb is not essential and that the invention can be applied equally as well to blown glass bulbs with the same light gain realized in principle;

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An'electric lamp comprising a sealed glass envelope having a concave rear reflector portion and an opposed concave front reflector portion, said rear reector portion having a reflecting surface of revolution adapted to redirect light rays from alight source at an optical focus of said reflecting surface into a converging beam of light, said front portion having a reecting surface of spheroidal shape with its center of curvature approximately coincident with the said focus of the rear reflecting surface, said front portion further having a central light-transmissive window proportioned to transmit therethrough substantially the full cone of light reflected from the rear reflecting surface, a concentrated light source disposed in said envelope approximately at the said focus of the rear reflecting surface, and leadingin wires sealed through the said front portion of the envelope at locations outwardly of said win- 4 dow and being connected to and supporting the said light source.

2. An electric lamp comprising a sealed glass envelope consisting of a preformed concave rear reflector section and a preformed concave front reflector section fusion-sealed together around their peripheries in opposed relation, said rear reflector section having an ellipsoidal reflecting surface and said front reflector section having a` reflecting surface of spheroldal shape with its center of curvature approximately coincident with the near focus of the ellipsoidal rear reflecting surface, said front reflector section further .f having a central light-transmissive window proportioned to transmit therethrough substantially the full cone of light reflected from the ellipsoidal rear reflecting surface, a concentrated light source disposed in said envelope approximately at the near focus of the ellipsoidal rear reflecting surface, and leading-in wires sealed through the said front reflector section at locations outwardly of said window and being connected to and supporting the said light source.

3. An electric lamp' comprising a sealed glass envelope consisting of a preformed concave rear reector section and a preformed concave front reector sectionfusion-sealed together around their peripheries in opposed relation, said rear reflector section having an ellipsoidal reflecting surface and said front reflector section having a reflecting surface of spheroldal shape with its center of curvature approximately coincident with the near focus of the ellipsoidal rear reiectingsurface, the said ellipsoidal and spheroidal reflecting surfaces' having substantially the same peripheral diameter and extending into substantial meeting relation with each other at their peripheries to conjointly form an approximately continuous reflecting surface, said front reflector section further having a central light-transmissive window proportioned to transmit therethrough substantially the full cone of light refiected from the ellipsoidal rear reiiecting surface, a concentrated light source disposed in said en, velope approximately at the near focus of the ellipsoidal rear reecting surface, and a pair of leading-in wires sealed through the said front reiiector section at locations on diametrically opposite sides of and outwardly of said window, said leading-in wires being connected to and supporting the said `light source.

LEO HENRICUS VERBEEK. GERARDUS HERMAN GERRITSMA.

No references cited. 

